[44] A. W. Bitting, _U.S. Dept. of Agric., Bull. 196_, 1915. [45] _U.S. Dept. of Agric., Report 97_, 1913. [46] Folin, _Preservatives and Other Chemicals in Foods_ (Harvard University Press, 1914), p. 32. [47] Folin, _op. cit._, p. 42. [48] See _U.S. Dept. of Agric., Report 94_, 1911. CHAPTER V FOOD-BORNE PATHOGENIC BACTERIA Many cases of so-called food poisoning are due to the presence of pathogenic bacteria in the food. In some instances, as in the typical meat poisoning epidemics, symptoms develop so soon after eating that the particular food involved is immediately suspected and laid hands on. In other cases the guilty article of food is difficult to trace. Certain cases of tuberculosis are undoubtedly caused by swallowing tubercle bacilli in the food, but the precise source and date of infection can be rarely, if ever, certainly established. The presence of pathogenic bacteria in food is usually due either to the contamination of the food by infected human beings during the process of preparation or serving, or to an infection of the animal from which the food is derived. The relative importance of these two factors is quite different in the various infections. TYPHOID FOOD INFECTION The typhoid bacillus does not attack any of the domestic animals; consequently all food-borne typhoid is caused more or less directly by human contamination. A remarkable instance of typhoid infection due to food was reported in 1914 in Hanford, California, where ninety-three typhoid cases were caused by eating Spanish spaghetti served at a public dinner.[49] Investigation showed that this dish was prepared by a woman typhoid-carrier who was harboring living typhoid bacilli at the time she mixed the sauce for the spaghetti before baking. Further laboratory experiments indicated that the ordinary baking temperature at which the spaghetti was cooked was not only not sufficient to sterilize the food, but afforded a favorable opportunity for the bacteria in the interior of the mass to multiply. The infection of the food was consequently heavy and involved a very large proportion (57 per cent) of those present at the dinner.